isotherm
/ˈaɪ.səʊˌθɜː(ɹ)m/
"isotherm" is a 8-letter English headword indexed on PlainSpell.
The verdict
“isotherm” is uncommon English (frequency #98,274 among 17,902 “I” headwords), classed as a noun. The kind of spelling people second-guess.
- #98,274
- frequency rank, English
- 17,902
- “I” headwords
According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - A line on a graph or chart, such as a weather map, along which all the points have the same temperature.
Corpus desk
Index EN-isotherm · isotherm · English
isotherm · rank #98,274 · 0 variants · 0 confusables
- FREQ-RARE #98,274
- LEN-LONG 8 letters
- VOW-3 3 vowels
- CONFUS-0 No pairs
- VAR-0 0 variants
- BOOK-DENSE 17,902
- PHOTO-FINISH isoniazid
Nearest frequency peer: isoniazid (-1 rank slots)
Read with this headword: Spelling guide for this pattern
Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.
Frequency neighbourhood for “isotherm”
Lower corpus rank = more everyday usage (inverted bar length for readability)
- Ioannis
Ioannis
1,732 corpus weight
- irrelevancy
irrelevancy
1,731 corpus weight
- irritatingly
irritatingly
1,730 corpus weight
- isoniazid
isoniazid
1,728 corpus weight
- isotherm
isotherm
1,727 corpus weight
- Isère
Isère
1,726 corpus weight
What this shows Bars show where “isotherm” sits against the nearest ranked English headwords in the FrequencyWords band, not a reprint of letter-browse containment.
| Property | Value |
|---|---|
| Headword | isotherm |
| Language | English |
| Part of speech | Noun |
| IPA | /ˈaɪ.səʊˌθɜː(ɹ)m/ |
| Letters | 8 |
| Frequency rank | #98,274 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Where “isotherm” sits in English frequency
Rare enough to double-check
isotherm is uncommon English at frequency #98,274 among 17,902 “I” headwords, classed as anoun, transcribed /ˈaɪ.səʊˌθɜː(ɹ)m/. Rarity is why readers land here mid-draft. Gloss: "A line on a graph or chart, such as a weather map, along which all the points have the same temperature.".
We couldn't generate a plausible misspelling set for isotherm, typically a sign the spelling maps closely to how the word sounds. Our confusable-pair dataset has no match for it, a sign it's visually distinctive enough not to be mixed up with another word.
Etymologically, the entry records: From the French isotherme (“of equal temperature”, adjective), itself from Ancient Greek ἴσος (ísos, “equal”) + θέρμη (thérmē, “warmth”). By surface analysis, iso- + -therm. The correct English form is isotherm, spelled I-S-O-T-H-E-R-M.
Definition
- 1A line on a graph or chart, such as a weather map, along which all the points have the same temperature.
Etymology
From the French isotherme (“of equal temperature”, adjective), itself from Ancient Greek ἴσος (ísos, “equal”) + θέρμη (thérmē, “warmth”). By surface analysis, iso- + -therm.
This word in other languages
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.
PlainSpell is rendered directly from structured Wiktionary extracts and open word-frequency lists, no number is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of May 6, 2026. Primary sources: Wiktionary (via kaikki.org) and FrequencyWords.
Frequently Asked Questions
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Similar English words by spelling shape
Same letter count and similar misspelling depth for "isotherm", not the corpus desk frequency band.
Same letter count
Frequency-ranked English headwords with 8 letters (nearest by frequency rank).
Data Source
Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.